Intracellular sodium homeostasis in rat hippocampal astrocytes.

Abstract

1. We determined the intracellular Na+ concentration ([Na+]

Mechanisms of H+and Na+Changes Induced by Glutamate, Kainate, and d-Aspartate in Rat Hippocampal Astrocytes

“…In agreement with an earlier study (Rose and Ransom, 1996), baseline [Na ϩ ] i in hippocampal astrocytes was about 15 mM in standard saline (Table 1). Application of either Glu, K A, or D-Asp rapidly increased [Na ϩ ] i within 30 -60 sec, followed by a recovery to baseline within 10 min (shown for Glu in Figs.…”

“…Solutions for calibration of SBFI's sensitivity to [Na ϩ ] i contained (in mM): 150 (K ϩ ϩ Na ϩ ), 30 Cl Ϫ , 120 gluconic acid, 1 MgSO 4 , 10 HEPES, adjusted to pH 7.2 with KOH. Gramicidin (3 M), monensin (10 M), and ouabain (1 mM), were used to equilibrate extra-and intracellular Na ϩ (Rose and Ransom, 1996). Dye loading.…”

“…Every three to four experiments, we checked for the accuracy of this calibration procedure by performing a two-point calibration with solutions titrated to pH 7.2 and 7.4. As described in detail by Rose and Ransom (1996), the 345/385 nm ratio of intracellular SBFI changes monotonically in hippocampal astrocytes with changes in [Na ϩ ] i between 0 and 50 mM. For intracellular calibration of [Na ϩ ] i , cells were therefore perfused with two or three calibration solutions (containing gramicidin, monensin, and ouabain) (see above) with different Na ϩ concentrations (0, 30, and 50 mM Na ϩ ); this was done at the end of each experiment.…”

“…In CO 2 / HCO 3 Ϫ -free saline, baseline [Na ϩ ] i decreased significantly to 11.9 mM (Table 1), indicating a contribution of inwardly directed Na ϩ / HCO 3 Ϫ cotransport and/or Na ϩ -dependent Cl Ϫ / HCO 3 Ϫ exchanger to baseline [Na ϩ ] i in these cells under standard conditions (Rose and Ransom, 1996). Both Glu-and K A-induced [Na ϩ ] i increases were slightly reduced in comparison to CO 2 / HCO 3 Ϫ -buffered saline (p Յ 0.025) ( Table 1).…”

Introduction: Special Issue in Honor of Bruce Ransom

“…Bob Fern contributes here on The Leukocentric Theory of Neurological Disorder: a Manifesto. Lastly, with Christine Rose, a series of papers analyzed intracellular sodium homeostasis and activityrelated fluctuations in astrocytes [24] and neurons [25]. Christine has continued to study the role of sodium in glia and reports on that topic in this issue, Astrocyte Sodium…”